Photocatalytic doping of organic semiconductors.

Chemical doping is an important approach to manipulating charge-carrier concentration and transport in organic semiconductors (OSCs)1-3 and ultimately enhances device performance4-7. However, conventional doping strategies often rely on the use of highly reactive (strong) dopants8-10, which are consumed during the doping process. Achieving efficient doping with weak and/or widely accessible dopants under mild conditions remains a considerable challenge. Here, we report a previously undescribed concept for the photocatalytic doping of OSCs that uses air as a weak oxidant (p-dopant) and operates at room temperature. This is a general approach that can be applied to various OSCs and photocatalysts, yielding electrical conductivities that exceed 3,000 S cm-1. We also demonstrate the successful photocatalytic reduction (n-doping) and simultaneous p-doping and n-doping of OSCs in which the organic salt used to maintain charge neutrality is the only chemical consumed. Our photocatalytic doping method offers great potential for advancing OSC doping and developing next-generation organic electronic devices.

Transition metal-catalysed molecular n-doping of organic semiconductors.

Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices1-9. N(electron)-doping is fundamentally more challenging than p(hole)-doping and typically achieves a very low doping efficiency (η) of less than 10%1,10. An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability1,5,6,9,11, which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd2(dba)3) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased η in a much shorter doping time and high electrical conductivities (above 100 S cm-1; ref. 12). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications12, 13.

A Highly Conductive n-Type Conjugated Polymer Synthesized in Water.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a benchmark hole-transporting (p-type) polymer that finds applications in diverse electronic devices. Most of its success is due to its facile synthesis in water, exceptional processability from aqueous solutions, and outstanding electrical performance in ambient. Applications in fields like (opto-)electronics, bioelectronics, and energy harvesting/storage devices often necessitate the complementary use of both p-type and n-type (electron-transporting) materials. However, the availability of n-type materials amenable to water-based polymerization and processing remains limited. Herein, we present a novel synthesis method enabling direct polymerization in water, yielding a highly conductive, water-processable n-type conjugated polymer, namely, poly[(2,2'-(2,5-dihydroxy-1,4-phenylene)diacetic acid)-stat-3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione] (PDADF), with remarkable electrical conductivity as high as 66 S cm-1, ranking among the highest for n-type polymers processed using green solvents. The new n-type polymer PDADF also exhibits outstanding stability, maintaining 90% of its initial conductivity after 146 days of storage in air. Our synthetic approach, along with the novel polymer it yields, promises significant advancements for the sustainable development of organic electronic materials and devices.

Tailoring the Molecular Planarity of Perylene Diimide-Based Third Component toward Efficient Ternary Organic Solar Cells.

Incorporating a third component into binary organic solar cells (b-OSCs) has provided a potential platform to boost power conversion efficiency (PCEs). However, gaining control over the non-equilibrium blend morphology via the molecular design of the perylene diimide (PDI)-based third component toward efficient ternary organic solar cells (t-OSCs) still remains challenging. Herein, two novel PDI derivatives are developed with tailored molecular planarity, namely ufBTz-2PDI and fBTz-2PDI, as the third component for t-OSCs. Notably, after performing a cyclization reaction, the twisted ufBTz-2PDI with an amorphous character transferred to the highly planar fBTz-2PDI followed by a semi-crystalline character. When incorporating the semi-crystalline fBTz-2PDI into the D18:L8-BO system, the resultant t-OSC achieved an impressive PCE of 18.56%, surpassing the 17.88% attained in b-OSCs. In comparison, the addition of amorphous ufBTz-2PDI into the binary system facilitates additional charge trap sites and results in a deteriorative PCE of 14.37%. Additionally, The third component fBTz-2PDI possesses a good generality in optimizing the PCEs of several b-OSCs systems are demonstrated. The results not only provided a novel A-DA'D-A motif for further designing efficient third component but also demonstrated the crucial role of modulated crystallinity of the PDI-based third component in optimizing PCEs of t-OSCs.

PC71BM as Morphology Regulator for Highly Efficient Ternary Organic Solar Cells with Bulk Heterojunction or Layer-by-Layer Configuration.

The ternary strategy is one of the effective methods to regulate the morphology of the active layer in organic solar cells (OSCs). In this work, the ternary OSCs with bulk heterojunction (BHJ) or layer-by-layer (LbL) active layers are prepared by using the polymer donor PM6 and the non-fullerene acceptor L8-BO as the main system and the fullerene acceptor PC71BM as the third component. The power conversion efficiencies (PCEs) of BHJ OSCs and LbL OSCs are increased from 17.10% to 18.02% and from 17.20% to 18.20% by introducing PC71BM into the binary active layer, respectively. The in situ UV-vis absorption spectra indicate that the molecular aggregation and crystallization process can be prolonged by introducing PC71BM into the PM6:L8-BO or PM6/L8-BO active layer. The molecular orientation and molecular crystallinity in the active layer are optimized by introducing the PC71BM into the binary BHJ or LbL active layers, which can be confirmed by the experimental results of grazing incidence wide-angle X-ray scattering. This study demonstrates that the third component PC71BM can be used as a morphology regulator to regulate the morphology of BHJ or LbL active layers, thus effectively improving the performance of BHJ and LbL OSCs.

Highly Efficient Organic Solar Cells with the Highly Crystalline Third Component as a Morphology Regulator.

The morphology of the active layer is crucial for highly efficient organic solar cells (OSCs), which can be regulated by selecting a rational third component. In this work, the highly crystalline nonfullerene acceptor BTP-eC9 is selected as the morphology regulator in OSCs with PM6:BTP-BO-4Cl as the main system. The addition of BTP-eC9 can prolong the nucleation and crystallization progress of acceptor and donor molecules, thereby enhancing the order of molecular arrangement. Meanwhile, the nucleation and crystallization time of the donor is earlier than that of the acceptors after introducing BTP-eC9, which is beneficial for obtaining a better vertical structural phase separation. The exciton dissociation, charge transport, and charge collection are promoted effectively by the optimized morphology of the active layer, which improves the short-circuit current density and filling factor. After introducing BTP-eC9, the power conversion efficiencies (PCEs) of the ternary OSCs are improved from 17.31% to 18.15%. The PCE is further improved to 18.39% by introducing gold nanopyramid (Au NBPs) into the hole transport layer to improve photon utilization efficiency. This work indicates that the morphology can be optimized by selecting a highly crystalline third component to regulate the nucleation and crystallization progress of the acceptor and donor molecules.

Simple and Efficient Synthesis of Novel Tetramers with Enhanced Glass Transition Temperature for High-Performance and Stable Organic Solar Cells.

Oligomer acceptors in organic solar cells (OSCs) have garnered substantial attention owing to their impressive power conversion efficiency (PCE) and long-term stability. However, the simple and efficient synthesis of oligomer acceptors with higher glass transition temperatures (Tg ) remains a formidable challenge. In this study, we propose an innovative strategy for the synthesis of tetramers, denoted as Tet-n, with elevated Tg s, achieved through only two consecutive Stille coupling reactions. Importantly, our strategy significantly reduces the redundancy in reaction steps compared to conventional methods for linear tetramer synthesis, thereby improving both reaction efficiency and yield. Furthermore, the OSC based on PM6:Tet-1 attains a high PCE of 17.32 %, and the PM6:L8-BO:Tet-1 ternary device achieves an even more higher PCE of 19.31 %. Remarkably, the binary device based on the Tet-1 tetramer demonstrates outstanding operational stability, retaining 80 % of the initial efficiency (T80 ) even after 1706 h of continuous illumination, which is primarily attributed to the enhanced Tg (247 °C) and lower diffusion coefficient (1.56×10-27  cm2 s-1 ). This work demonstrates the effectiveness of our proposed approach in the straightforward and efficient synthesis of tetramers materials with higher Tg s, thus offering a viable pathway for developing high-efficiency and stable OSCs.

Multi-Selenophene Incorporated Thiazole Imide-Based n-Type Polymers for High-Performance Organic Thermoelectrics.

Developing polymers with high electrical conductivity (σ) after n-doping is a great challenge for the advance of the field of organic thermoelectrics (OTEs). Herein, we report a series of thiazole imide-based n-type polymers by gradually increasing selenophene content in polymeric backbone. Thanks to the strong intramolecular noncovalent N⋅⋅⋅S interaction and enhanced intermolecular Se⋅⋅⋅Se interaction, with the increase of selenophene content, the polymers show gradually lowered LUMOs, more planar backbone, and improved film crystallinity versus the selenophene-free analogue. Consequently, polymer PDTzSI-Se with the highest selenophene content achieves a champion σ of 164.0 S cm-1 and a power factor of 49.0 µW m-1 K-2 in the series when applied in OTEs after n-doping. The σ value is the highest one for n-type donor-acceptor OTE materials reported to date. Our work indicates that selenophene substitution is a powerful strategy for developing high-performance n-type OTE materials and selenophene incorporated thiazole imides offer an excellent platform in enabling n-type polymers with high backbone coplanarity, deep-lying LUMO and enhanced mobility/conductivity.

High-performance n-Type Organic Thermoelectrics with Exceptional Conductivity by Polymer-Dopant Matching.

Achieving high electrical conductivity (σ) and power factor (PF) simultaneously remains a significant challenge for n-type organic themoelectrics (OTEs). Herein, we demonstrate the state-of-the-art OTEs performance through blending a fused bithiophene imide dimer-based polymer f-BTI2g-SVSCN and its selenophene-substituted analogue f-BSeI2g-SVSCN with a julolidine-functionalized benzimidazoline n-dopant JLBI, vis-à-vis when blended with commercially available n-dopants TAM and N-DMBI. The advantages of introducing a more lipophilic julolidine group into the dopant structure of JLBI are evidenced by the enhanced OTEs performance that JLBI-doped films show when compared to those doped with N-DMBI or TAM. In fact, thanks to the enhanced intermolecular interactions and the lower-lying LUMO level enabled by the increase of selenophene content in polymer backbone, JLBI-doped films of f-BSeI2g-SVSCN exhibit a unprecedent σ of 206 S cm-1 and a PF of 114 µW m-1 K-2. Interestingly, σ can be further enhanced up to 326 S cm-1 by using TAM dopant as a consequence of its favorable diffusion behavior into densely packed crystalline domains. These values are the highest to date for solution-processed molecularly n-doped polymers, demonstrating the effectiveness of the polymer-dopant matching approach carried out in this work.

Cyano-Functionalized Pyrazine: A Structurally Simple and Easily Accessible Electron-Deficient Building Block for n-Type Organic Thermoelectric Polymers.

Developing low-cost and high-performance n-type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron-deficient building blocks with simple structure and easy synthesis, which are essential for the development of n-type polymer semiconductors. Herein, we synthesized two cyano-functionalized highly electron-deficient building blocks, namely 3,6-dibromopyrazine-2-carbonitrile (CNPz) and 3,6-Dibromopyrazine-2,5-dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one-step reaction and three-step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor-acceptor (A-A) polymers, P(DPP-CNPz) and P(DPP-DCNPz) are successfully developed, featuring deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels, which are beneficial to n-type organic thin-film transistors (OTFTs) and OTEs performance. An optimal unipolar electron mobility of 0.85 and 1.85 cm2 V-1 s-1 is obtained for P(DPP-CNPz) and P(DPP-DCNPz), respectively. When doped with N-DMBI, P(DPP-CNPz) and P(DPP-DCNPz) show high n-type electrical conductivities/power factors of 25.3 S cm-1 /41.4 µW m-1 K-2 , and 33.9 S cm-1 /30.4 µW m-1 K-2 , respectively. Hence, the cyano-functionalized pyrazine CNPz and DCNPz represent a new class of structurally simple, low-cost and readily accessible electron-deficient building block for constructing n-type polymer semiconductors.

Functionalized Phenanthrene Imide-Based Polymers for n-Type Organic Thin-Film Transistors.

High-performing n-type polymers are crucial for the advance of organic electronics field, however strong electron-deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide-functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π-conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high-performance n-type polymers. Among the PAHs, phenanthrene (PhA) features a well-delocalized aromatic π-system with multiple modifiable active sites . However, the PhA-based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene-modified CPCNI exhibits a well stabilized LUMO energy level (-3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI, two polymers PCPOI-Tz and PCPCNI-Tz were developed. Applied to organic thin-film transistors, owing to the strong electron-deficiency of CPCNI, polymer PCPCNI-Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI-Tz. This work affords two structurally novel electron-deficient building blocks and highlights the effectiveness of dual functionalization of PhAs with strong electron-withdrawing groups for devising n-type polymers.

On-demand catalysed n-doping of organic semiconductors.

A new approach to control the n-doping reaction of organic semiconductors is reported using surface-functionalized gold nanoparticles (f-AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n-type dopant precursor N-DMBI-H with several molecular and polymeric semiconductors at different temperatures with/without f-AuNPs, vis-à-vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that f-AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~ 70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~ 10 - 140 S cm-1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions, will broaden the use of the corresponding n-doped films in opto-electronic devices such as thin-film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts.

Simplified Y6-Based Nonfullerene Acceptors: In-Depth Study on Molecular Structure-Property Relation, Molecular Dynamics Simulation, and Charge Dynamics.

Two new Y6 derivatives of symmetrical YBO-2O and asymmetrical YBO-FO nonfullerene acceptors (NFAs) are prepared with a simplified synthetic procedure by incorporating octyl and fluorine substituents onto the terminal 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN) moiety. By moving the alkyl substituents on the Y6 core to the terminal INCN moiety, the lowest unoccupied molecular orbital of the YBO NFAs increases without decreasing solubility, resulting in high open-circuit voltages of the devices. Molecular dynamics simulation shows that YBO-2O/-FO preferentially form core-core and terminal-terminal dimeric interactions, demonstrating their tighter packing structure and higher electron mobility than Y6, which is consistent with 2D grazing incidence X-ray scattering and space charge limited current measurements. In blend films, the hole transfer (HT) from YBO-2O/-FO to the polymer donor PM6 is studied in detail by transient absorption spectroscopy, demonstrating efficient HT from YBO-FO to PM6 with their suitable energy level alignment. Despite the simplified synthesis, YBO-FO demonstrates photovoltaic performance similar to that of Y6, exhibiting a power conversion efficiency of 15.01%. Overall, this design strategy not only simplifies the synthetic procedures but also adjusts the electrical properties by modifying the intermolecular packing and energy level alignment, suggesting a novel simplified molecular design of Y6 derivatives.

Synergistic Contribution of Oligo(ethylene glycol) and Fluorine Substitution of Conjugated Polymer Photocatalysts toward Solar Driven Sacrificial Hydrogen Evolution.

To separately explore the importance of hydrophilicity and backbone planarity of polymer photocatalyst, a series of benzothiadiazole-based donor-acceptor alternating copolymers incorporating alkoxy, linear oligo(ethylene glycol) (OEG) side chain, and backbone fluorine substituents is presented. The OEG side chains in the polymer backbone increase the surface energy of the polymer nanoparticles, thereby improving the interaction with water and facilitating electron transfer to water. Moreover, the OEG-attached copolymers exhibit enhanced intermolecular packing compared to polymers with alkoxy side chains, which is possibly attributed to the self-assembly properties of the side chains. Fluorine substituents on the polymer backbone produce highly ordered lamellar stacks with distinct π-π stacking features; subsequently, the long-lived polarons toward hydrogen evolution are observed by transient absorption spectroscopy. In addition, a new nanoparticle synthesis strategy using a methanol/water mixed solvent is first adopted, thereby avoiding the screening effect of surfactants between the nanoparticles and water. Finally, hydrogen evolution rate of 26 000 µmol g-1  h-1 is obtained for the copolymer incorporated with both OEG side chains and fluorine substituents under visible-light irradiation (λ > 420 nm). This study demonstrates how the glycol side chain strategy can be further optimized for polymer photocatalysts by controlling the backbone planarity.

Deciphering the Effects of Molecular Dipole Moments on the Photovoltaic Performance of Organic Solar Cells.

The dielectronic constant of organic semiconductor materials is directly related to its molecule dipole moment, which can be used to guide the design of high-performance organic photovoltaic materials. Herein, two isomeric small molecule acceptors, ANDT-2F and CNDT-2F, are designed and synthesized by using the electron localization effect of alkoxy in different positions of naphthalene. It is found that the axisymmetric ANDT-2F exhibits a larger dipole moment, which can improve exciton dissociation and charge generation efficiencies due to the strong intramolecular charge transfer effect, resulting in the higher photovoltaic performance of devices. Moreover, PBDB-T:ANDT-2F blend film exhibits larger and more balanced hole and electron mobility as well as nanoscale phase separation due to the favorable miscibility. As a result, the optimized device based on axisymmetric ANDT-2F shows a JSC of 21.30 mA cm-2 , an FF of 66.21%, and a power conversion energy of 12.13%, higher than that of centrosymmetric CNDT-2F-based device. This work provides important implications for designing and synthesizing efficient organic photovoltaic materials by tuning their dipole moment.

Semiconducting Polymers Based on Simple Electron-Deficient Cyanated trans-1,3-Butadienes for Organic Field-Effect Transistors.

Developing high-performance but low-cost n-type polymers remains a significant challenge in the commercialization of organic field-effect transistors (OFETs). To achieve this objective, it is essential to design the key electron-deficient units with simple structures and facile preparation processes, which can facilitate the production of low-cost n-type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans-1,3-butadiene, we developed a series of structurally simple but highly electron-deficient building blocks, namely 1,4-dicyano-butadiene (CNDE), 3-fluoro-1,4-dicyano-butadiene (CNFDE), and 2,3-difluoro-1,4-dicyano-butadiene (CNDFDE), featuring a highly coplanar backbone and deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels (-3.03-4.33 eV), which render them highly attractive for developing n-type semiconducting polymers. Notably, all these electron-deficient units can be easily accessed by a two-step high-yield synthetic procedure from low-cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerization with diketopyrrolopyrrole (DPP), three copolymers were developed that demonstrated unipolar n-type transport characteristics in OFETs with the highest electron mobility of >1 cm2  V-1 s-1 . Hence, CNDE, CNFDE, and CNDFDE represent a class of novel, simple, and efficient electron-deficient units for constructing low-cost n-type polymers, thereby providing valuable insight for OFET applications.

Double Asymmetric Core Optimizes Crystal Packing to Enable Selenophene-based Acceptor with Over 18 % Efficiency in Binary Organic Solar Cells.

Side-chain tailoring is a promising method to optimize the performance of organic solar cells (OSCs). However, asymmetric alkyl chain-based small molecular acceptors (SMAs) are still difficult to afford. Herein, we adopted a novel asymmetric n-nonyl/undecyl substitution strategy and synthesized two A-D1 A'D2 -A double asymmetric isomeric SMAs with asymmetric selenophene-based central core for OSCs. Crystallographic analysis indicates that AYT9Se11-Cl forms a more compact and order intermolecular packing compared to AYT11Se9-Cl, which contributed to higher electron mobility in neat AYT9Se11-Cl film. Moreover, the PM6 : AYT9Se11-Cl blend film shows a better morphology with appropriate phase separation and distinct face-on orientation than PM6 : AYT11Se9-Cl. The OSCs with PM6 : AYT9Se11-Cl obtain a superior PCE of 18.12 % compared to PM6 : AYT11Se9-Cl (17.52 %), which is the best efficiency for the selenium-incorporated SMAs in binary BHJ OSCs. Our findings elucidate that the promising double asymmetric strategy with isomeric alkyl chains precisely modulates the crystal packing and enhances the photovoltaic efficiency of selenophene-incorporated SMAs.

Optimized Crystal Framework by Asymmetric Core Isomerization in Selenium-Substituted Acceptor for Efficient Binary Organic Solar Cells.

Both the regional isomerization and selenium-substitution of the small molecular acceptors (SMAs) play significant roles in developing efficient organic solar cells (OSCs), while their synergistic effects remain elusive. Herein, we developed three isomeric SMAs (S-CSeF, A-ISeF, and A-OSeF) via subtly manipulating the mono-selenium substituted position (central, inner, or outer) and type of heteroaromatic ring on the central core by synergistic strategies for efficient OSCs, respectively. Crystallography of asymmetric A-OSeF presents a closer intermolecular π-π stacking and more ordered 3-dimensional network packing and efficient charge-hopping pathways. With the successive out-shift of the mono-selenium substituted position, the neat films give a slightly wider band gap and gradually higher crystallinity and electron mobility. The PM1 : A-OSeF afford favourable fibrous phase separation morphology with more ordered molecular packing and efficient charge transportation compared to the other two counterparts. Consequently, the A-OSeF-based devices achieve a champion efficiency of 18.5 %, which represents the record value for the reported selenium-containing SMAs in binary OSCs. Our developed precise molecular engineering of the position and type of selenium-based heteroaromatic ring of SMAs provides a promising synergistic approach to optimizing crystal stacking and boosting top-ranked selenium-containing SMAs-based OSCs.

On the Conformation of Dimeric Acceptors and Their Polymer Solar Cells with Efficiency over 18 .

The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular π-π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs.

Ionic Dopant-Free Polymer Alloy Hole Transport Materials for High-Performance Perovskite Solar Cells.

The dominated hole transport material (HTM) used in state-of-the-art perovskite solar cells (PSCs) is Spiro-OMeTAD, which needs to be doped to improve its conductivity and mobility. The inevitable instability induced by deliquescent dopants and the necessary oxidation process in air hinders the commercialization of this technology. Here, an alloy strategy using two conjugated polymers with highly similar structures but different crystallinities for dopant-free HTM and high-performance PSCs has been demonstrated. We found that the polymeric packing and crystallinity of a polymer alloy could be regulated finely by blending the polymer PM6 and our developed polymer PMSe, which exhibits a shorter π-π stacking distance due to the improved planarity of the polymer backbone with strong C═O···Se noncovalent interactions. The structure-property relationship of the polymer alloy is investigated by theoretical and experimental analyses. The optimized PSCs using the polymer alloy HTM without any ionic dopants feature an excellent power conversion efficiency of 24.53% and a high open circuit voltage (VOC) of 1.19 V with much improved stability. This efficiency is much higher than that of the control device using doped Spiro-OMeTAD HTM (PCE = 22.54%). Our work provides a very effective strategy to design and construct dopant-free hole transport materials for highly efficient perovskite solar cells and other applications.